Peer Revenue Fully funded

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics

Watch Physics

Monday 15 June

Quantum Physics

Optimizing resource bounds in direct fidelity estimation

Netanel Barel, Lee Peleg, Yotam Kadish et al. (+2 more)

Direct fidelity estimation provides a way to estimate the fidelity between an experimentally prepared state and a desired pure target state without performing full tomography. Two influential formulations were introduced in 2011 by Flammia and Liu and by da Silva, Landon-Cardinal, and Poulin. In these protocols, the total estimation error is controlled through two distinct probabilistic steps: first, the fidelity is approximated using randomly sampled Pauli observables; second, each sampled expectation value is estimated from finitely many measurement outcomes. In this work we show that additional structural information about the noise can substantially sharpen the corresponding resource bounds. In particular, for some canonical channels the effective number of sampled Pauli settings can be reduced, leading to lower measurement cost both in the general pure-state setting and in the case of a stabilizer state. These results illustrate a broader point: worst-case confidence bounds in direct fidelity estimation can be significantly conservative when experimentally relevant structure is ignored. As a technical ingredient, we also revisit the allocation of the total accuracy and confidence budgets between the two probabilistic steps. Reformulating the analysis in terms of separate error parameters yields a constrained optimization problem whose solution lowers the average number of measurements in the general pure-state setting. Numerical simulations based on quantum circuits implemented in Qiskit illustrate both the improvement obtained under structured-noise assumptions and the conservativeness of the original worst-case bounds.
Read the full abstract

All authors Netanel Barel, Lee Peleg, Yotam Kadish, Amit Ben Kish, Yotam Shapira

Optics

Integrated tunable mid-infrared electro-optic frequency comb generator based on nonlinear conversion

Pierre Didier, Prakhar Jain, Tristan Kuttner et al. (+2 more)

Mid-infrared frequency combs enable highly selective and sensitive molecular spectroscopy by leveraging the strong vibrational transitions in this spectral region. Among these, there is a particular need for compact, tunable sources with electronic control over comb parameters for integrated sensing platforms. In this work, we demonstrate a mid-infrared electro-optic frequency comb source based on nonlinear frequency conversion in thin film lithium niobate. The system combines a near-infrared pump, amplitude-modulated using an integrated Mach-Zehnder modulator for lock-in detection, with a telecom-band electro-optic comb generated via a double-pass phase modulation scheme. Mid-infrared comb generation is achieved through difference frequency generation in a periodically poled waveguide. By tuning the telecom seed laser and the chip temperature, we obtain mid-infrared combs with a bandwidth of approximately 6 nm and center wavelength tunability of over 200 nm. The comb free spectral range is directly controlled via the applied radio-frequency modulation. Operation across multiple integrated photonic circuits reaching wavelengths up to 3.7 $\mu$m is demonstrated. Furthermore, dual-tone EO comb generation in the mid-infrared is realized. To our knowledge, this is the first integrated mid-infrared electro-optic comb source offering independent electronic control of both center wavelength and comb spacing.
Read the full abstract

All authors Pierre Didier, Prakhar Jain, Tristan Kuttner, Oliver Pitz, Rachel Grange

Materials Science

Implementation of rotational invariance for first-principles phonons and application to low-dimensional materials

Benoit Van Troeye, Xavier Gonze and Geoffrey Pourtois

The acoustic flexural (phonon) modes of low-dimensional materials should show a quadratic dispersion close to the Brillouin zone center. Any departure from this behavior in Density Functional Theory calculations is typically associated with a breaking of the rotational invariance, with few methods available to correct it. In this work, we reexamine this issue based on a reciprocal-space imposition of this condition, with corrections on the zone-center IFCs and their first and second derivatives with respect to the phonon wavevector. We propose two correction schemes for the short-range part of the interatomic force constants, one based on the Moore-Penrose pseudoinverse, that we implement in the ABINIT software package, and one based on the straight modification of the on-site antisymmetric part of the first-order derivative of the dynamical matrix with respect to the wavevector. We investigate the impact of imposing rotational invariance for different system dimensionalities and pseudopotentials. Finally, we discuss rotational invariance in the context of long-range electrostatics contribution to the IFCs. We observe that the usual treatment of electrostatics is by construction not rotationally invariant. This is found especially critical when correcting the second derivatives of the IFCs.
Read the full abstract

Statistical Mechanics

Endoreversible Carnot machines with long-time reversible limit

Ramandeep S. Johal and Rajeshree Chakraborty

The well-known Curzon-Ahlborn (CA) engine [Am. J. Phys. 43, 22 (1975)] runs in finite time and yields a finite power output. In order to recover the standard Carnot cycle from the CA model, the limit of quasi-static operation has to be concurrent with the reversible limit, a condition strangely missing from the CA model. We augment this model by specifying the duration of the isothermal process as a monotonic decreasing function of the temperature difference between the working substance and the reservoir. As an illustration, we analyze the machine's operation in the low-dissipation (LD) regime in which the entropy production in each isothermal branch is inversely proportional to the duration of the process. The modified model, while retaining the optimal features of the CA model, also yields explicit expressions for the optimal durations of isothermal processes. We compare the optimal cycle periods of the present model and the LD model, and show their agreement in the linear response regime.
Read the full abstract

Statistical Mechanics

Foundations of entropy in complex systems

Jan Korbel

This chapter reviews the foundations of entropy and their extensions to complex systems. We first discuss the relation between Boltzmann's formula, multiplicity, coarse-graining, and Shannon entropy, before introducing generalized entropies such as Rényi, Tsallis, and Burg entropy. We then examine Maxwell–Boltzmann, Bose–Einstein, and Fermi–Dirac statistics, structure-forming systems, sample-space reducing processes, Pólya urns, and nonlinear dynamics. Axiomatic approaches are presented through the Shannon–Khinchin axioms, Tempesta group-composability, Hanel–Thurner asymptotic scaling, Shore–Johnson consistency axioms, and Lieb–Yngvason axioms. Finally, we discuss calibration invariance, Hanel–Thurner–Gell-Mann duality between linear and escort averages, and Kolmogorov–Nagumo averages, showing how the same distribution can arise from different entropies, constraints, or dynamics. These results emphasize that the choice of entropy should be guided by the structure and physical properties of the system.
Read the full abstract

Optics

Neural network inverse design of nanophotonic scintillators

Nathan Regev, Avner Shultzman, Francis Loignon-Houle et al. (+2 more)

Scintillators are materials converting high-energy radiation into optical light, essential in a range of technologies such as medical imaging systems and security scanners. Scintillator development and optimization have remained limited by the complexity of their underlying physics, involving stochastic cascades of electron-electron, electron-phonon, and electron-photon interactions. Such processes are typically modeled by non-differentiable Monte Carlo simulations, limiting the applicability of machine learning for scintillator development. Here we present a physics-informed neural network that learns the scintillation cascade process from the incident high-energy particle to photon emission, substantially accelerating scintillator design and optimization. Combining this neural network with photonic simulations enables end-to-end differentiable optimization of the scintillator geometry. This allows us to optimize for arbitrary figures of merit, such as specific target emission patterns.. We demonstrate the concept and characterize it relative to previous approaches by inverse design of nanophotonic scintillators for X-ray imaging.
Read the full abstract

All authors Nathan Regev, Avner Shultzman, Francis Loignon-Houle, Charles Roques-Carmes, Ido Kaminer

Optics

Writing and readout of luminescent defects on an optical nanofiber using an electron beam

Yining Xuan and Mark Sadgrove

We demonstrate the writing and readout of groups of luminescent defects on an optical nanofiber (ONF), with readout performed through the fiber modes. In the write step, a focused electron beam incident on the fiber surface created luminescent defect centers in the fiber's silica in a region of diameter $\sim200$ nm localized about the beam center. In the readout step, the electron beam was scanned over the fiber and the induced cathodoluminescence from the defects was coupled into the ONF and detected. The regions with electron beam-induced luminescent defects exhibited a strongly enhanced optical signal, despite minimal observable change in the fiber surface, as judged by secondary electron imaging over the same region. Spectral measurements show that the enhanced luminescence stems from the creation of both oxygen deficiency centers (ODCs) and non-bridging oxygen hole centers (NBOHCs) by the electron beam.
Read the full abstract

Astrophysics of Galaxies

Groups of Dwarf Galaxies in the Local Universe

Sanjaya Paudel, Cristiano G. Sabiu, Suk-Jin Yoon et al. (+3 more)

We present a systematic search for dwarf-galaxy groups in the local Universe ($z<0.02$), identifying 28 systems containing at least four spectroscopically confirmed members selected from the SDSS and DESI surveys. Group membership is assigned based on projected separation -within 300\,kpc from the most massive galaxy (designated the “central”) -and a relative line-of-sight velocity difference of less than 200\,km/s. The sample has a median redshift of $z=0.0131$ ($\sim55$\,Mpc) and a median central stellar mass of $1.7\times10^{9}\,M_\odot$, firmly placing these systems in the low-mass regime. In total, 28 groups contain 129 dwarf galaxy members, with a median stellar mass of $1.63\times10^{8}\,M_\odot$. The median $r$-band apparent magnitude of the member dwarfs is 17.38\,mag, slightly fainter than the spectroscopic observation limit of the SDSS main spectroscopic survey. Remarkably, several groups are centered on galaxies with stellar masses as low as $\sim10^{8}\,M_\odot$, comparable to the Fornax dwarf spheroidal, demonstrating that even very faint galaxies can host bound satellite systems. Most groups exhibit low velocity dispersions ($\sigma_{v}<50$\,km/s), consistent with being gravitationally bound. The inferred dynamical masses span $\sim10^{10}-10^{12}\,M_\odot$, while the corresponding three-dimensional velocity dispersions ($\sigma_{3D}$) fall between 50 and 100\,\kms, characteristic of dynamically cold, low-mass halos. Our results provide empirical constraints on small-scale structure formation and show strong consistency with predictions from cosmological volume simulations, supporting the picture that dwarf galaxies can serve as central hosts for their own satellite systems embedded within extended dark-matter halos.
Read the full abstract

All authors Sanjaya Paudel, Cristiano G. Sabiu, Suk-Jin Yoon, Daya Nidhi Chhatkuli, Jaewon Yoo, Nau Raj Pokhrel

Cosmology and Nongalactic Astrophysics

Tomography of the gamma-ray sky from cross-correlation with DESI DR2 and unWISE galaxies

Alex Krolewski, Neal Dalal, Will J. Percival et al. (+39 more)

We study the origin of extragalactic gamma-ray emission observed by Fermi-LAT, using the cross-correlation of the gamma-ray sky with maps of large-scale structure provided by the DESI and unWISE surveys. Tomographic cross-correlation reveals the bias-weighted redshift distributions of gamma-ray sources. We first illustrate this method by cross-correlating detected gamma-ray point sources with large-scale structure. We find a significant cross-correlation and infer a point source redshift distribution broadly consistent with the distribution of identified optical counterparts previously reported in the literature, as well as a similar linear bias ($b \approx 2$) to massive galaxies that host bright active galactic nuclei. We then study the clustering of the Fermi unresolved gamma-ray background (UGRB), both in auto-correlation and in cross-correlation with large-scale structure. We detect the cross-correlation of the UGRB and LSS at $\sim 10\sigma$ in total, with highly significant detections from both DESI and unWISE. Our measurements suggest that the redshift distribution of the UGRB is broadly consistent with the redshift distribution of detected point sources. Additionally, we find a relatively weak amplitude for the cross-correlation with large-scale structure at z < 2, suggesting a significant fraction of the UGRB does not come from z < 2 large-scale structure. A natural candidate is contamination of from residual Galactic emission, and our best estimate of the contamination level derived from the UGRB auto-spectrum suggests that the mean bias of UGRB sources is indeed quite similar to the bias of detected Fermi point sources. However, we cannot exclude additional emission from gamma-ray sources at high redshift, z > 2, and we suggest that cross-correlation with tracers at z > 2, including CMB lensing, would be the ideal way to determine the fraction of z > 2 emission.
Read the full abstract

All authors Alex Krolewski, Neal Dalal, Will J. Percival, Elena Pinetti, J. Aguilar, S. Ahlen, S. BenZvi, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztanaga, S. Gontcho A Gontcho, G. Gutierrez, J. Guy, D. Huterer, M. Ishak, R. Joyce, A. Kremin, O. Lahav, M. Landriau, L. Le Guillou, M. E. Levi, M. Manera, A. Meisner, R. Miquel, A. D. Myers, S. Nadathur, F. Prada, I. Perez-Rafols, G. Rossi, E. Sanchez, D. Schlegel, J. Silber, D. Sprayberry, G. Tarle, B. A. Weaver

General Relativity and Quantum Cosmology

Ultraviolet Structure of the Gravitational-Wave Response in a Time-Dependent Scalar Medium

Han Lai and Atsuhisa Ota

We study the real-time linear response of gravitational waves in an FLRW background with a scalar field of general time-dependent effective mass. In the Schwinger-Keldysh formalism, we develop an adiabatic regularization scheme for unequal-time correlation functions and use it to extract the ultraviolet structure of the one-loop response. The leading divergence reproduces the familiar $\Box ^2h_{ij}$ structure, whereas the time-dependent background induces additional local divergences proportional to $\Box h_{ij}$, $\partial_\tau h_{ij}$, and $h_{ij}$. These are renormalized by local counterterms associated with the Weyl-squared term, a time-dependent Ricci-scalar term, a time-dependent cosmological constant, and the Ricci-scalar-squared term $R^2$. The same counterterms also remove the ultraviolet divergences of the background tadpole stress tensor and agree with the known covariant counterterm results. In a flat-background Mathieu oscillator example, replacing the adiabatic vacuum by the instantaneous vacuum leaves these counterterms unchanged but introduces an initial-surface divergence, which is absorbed into the initial data rather than the bulk counterterms.
Read the full abstract

Quantum Physics

Reconstruction of detector error model for quantum error correction

Cheng Ye and Pan Zhang

Fault-tolerant quantum computing fundamentally relies on the accurate characterization of circuit-level noise to optimize decoding algorithms. However, extracting complex multi-body error correlations remains challenging. Contemporary greedy inference algorithms can suffer from statistical distortion, discarding true physical mechanisms while introducing many unphysical false positives. Here, we introduce the Correlation-Analysis-based Hypergraph Reconstruction (CAHR) algorithm, a globally consistent framework to invert experimental syndrome statistics directly into discrete physical hypergraphs. By coupling exact algebraic correlation equations with a top-down concurrent-pruning strategy, CAHR recovers the fault topology without false positives for both $d=5$ rotated surface codes and dense 8-body 2D color codes in our benchmark settings. Furthermore, we show that exact continuous parameter extraction in dense codes is limited by a variance cascade, where absolute statistical variance accumulates linearly from high- to low-degree mechanisms. This motivates a two-stage inference paradigm: utilizing CAHR to extract the fault topology, followed by continuous probability optimization. This provides a practical approach for characterizing and decoding highly correlated noise in realistic quantum hardware.
Read the full abstract

High Energy Physics (Phenomenology)

Search for Invisibly Decaying Light Scalars at the FCC-ee

Aman Desai and Tania Robens

We investigate the production of invisibly decaying light scalars in association with hadronically decaying $Z$ bosons at the Future Circular Collider-ee at a centre-of-mass energy $\sqrt{s}=240$ GeV. Several new physics models predict the existence of these low-mass scalar states, while the existing experimental constraints do not yet exclude these states. We study the low-mass scalar based on a simplified extension of the Standard Model, introducing an additional scalar singlet and a scalar dark matter candidate. The analysis is performed for a set of new scalars with mass in the range $(15, 120)$ GeV, by employing a selection-based strategy complemented with Multivariate Analysis techniques to discriminate the signal from background. The expected upper limits on the production cross-section times the branching fraction of the new scalars decaying invisibly are evaluated as a function of the scalar mass. We find that sensitivities of $\sim 10^{-2}$–$10^{-1}$~fb are achievable for scalar masses below the $Z$ boson mass, while sensitivities of $0.1$–$1$~fb are obtained in the mass range 80–120 \GeV. Depending on the mixing angle, novel scalars with masses up to 80 \GeV are within discovery reach.
Read the full abstract

General Relativity and Quantum Cosmology

Gravitational waveforms from periodic orbits around Gauss-Bonnet black holes

Yi-Han Huang, Sen Guo, Yu Liang et al. (+2 more)

Extreme mass-ratio inspirals (EMRIs) constitute one of the most promising probes of strong field gravity for future space borne gravitational-wave observatories. As a representative higher-curvature extension of General Relativity (GR), four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity is distinguished by its strictly linear geometric coupling. By this mathematical property, the pathological Fisher-matrix singularities that typically plague conventional modified black hole models are effectively evaded, thereby providing an ideal framework to test topological deviations from classical spacetimes. Through the classification of equatorial periodic orbits via an integer taxonomy $(z,w,v)$, it is demonstrated that even modest Gauss-Bonnet couplings ($\alpha \sim 0.1M^2$) imprint measurable geometric signatures onto the zoom-whirl architecture. Although the global conservative energy budget is shifted by a mere $\sim 0.2\%$, the short-range repulsive EGB core severely alters the strong field whirl dynamics, whereby a resolvable macroscopic dephasing of several radians per orbit is accumulated. Through semi-relativistic waveform modeling, it is revealed that this temporal compression manifests as a rigid, high-frequency stretching of the gravitational-wave harmonic comb – a clean, amplitude-independent spectral signature ideally suited for detection by LISA, Taiji, and TianQin. A rigorous Fisher information analysis confirms that for a typical four-year observation at a signal-to-noise ratio of $\rho=20$, the marginalized error on the EGB coupling can be tightly bounded to $\sigma_\alpha \sim \mathcal{O}(10^{-6}) M^2$, with virtually negligible parameter degeneracy with the orbital eccentricity.
Read the full abstract

All authors Yi-Han Huang, Sen Guo, Yu Liang, Lin Wen, Kai Lin

Solar and Stellar Astrophysics

Investigation of Solar Wind Speed Characteristics Using IPS Observations and the PFSS+SCS Model

Kyogo Tokoro, Munehito Shoda and Shinsuke Imada

Understanding the relationship between solar wind speed and global coronal magnetic field is essential for space-weather forecasting and provides key diagnostics of the underlying acceleration mechanisms. Most observational studies to date have relied on near-ecliptic measurements dominated by slow wind, and the full range of wind speed, including fast wind, is insufficiently explored. Interplanetary scintillation (IPS) observations offer global coverage of wind speed; however, previous IPS-based studies have relied solely on the potential field source surface (PFSS) model, which does not adequately reproduce key features of the heliospheric magnetic field, potentially leading to the poor connectivity between the solar wind and its coronal source regions. Here we perform a comprehensive statistical analysis of the wind speed using IPS observations combined with PFSS and the Schatten current sheet (SCS) model. We find that the parameter f_SS/B_sun bifurcates the solar wind into two distinct groups: one showing a strong negative correlation and the other showing no correlation. This grouping is better organized by the footpoint magnetic field strength and the distance from coronal hole boundary (DCHB) than by solar magnetic activity, suggesting that the two groups may reflect fundamentally different acceleration mechanisms.
Read the full abstract

Astrophysics of Galaxies

The Milky Way's Missing In-Situ Halo

Madeline Lucey, Robyn E. Sanderson, Alexander H. Riley et al. (+3 more)

The Milky Way's stellar halo preserves a record of its mass assembly history, encoding accretion events in its structural properties. Among the most prominent of these features is a strong break in the halo density profile at $\approx$20-30 kpc, long attributed to the apocenter pile-up of stars from the Gaia-Enceladus/Sausage merger. However, whether this interpretation is consistent with state-of-the-art cosmological simulations remains unclear. In this work, we compare the Milky Way's measured stellar halo density profile between galactocentric radii of $1\unicode{x2013}100$ kpc to those of Milky Way-mass galaxies from the FIRE-2 and Auriga cosmological zoom-in simulation suites, spanning a total of 24 simulated galaxies. We find that simulated halo profiles are significantly steeper than Milky Way measurements within $\approx$15 kpc, and that profile breaks are rare in simulations and never as strong as the Milky Way's. Of the three galaxies with statistically significant breaks, only one exhibits a break attributable to apocenter pile-up of an accreted merger remnant. Decomposing the simulated profiles, we find that the accreted halo profiles are broadly consistent with Milky Way measurements, while the in-situ halo dominates within $\approx$20 kpc and drives the discrepancy. These results raise a compelling question: where is the Milky Way's in-situ halo? The origin of this tension may reflect systematic biases in current halo measurements, an overproduction of early spheroidal star formation in cosmological simulations, or more fundamental differences in the underlying physics (e.g., dark matter) governing the assembly and structure of the inner Galaxy.
Read the full abstract

All authors Madeline Lucey, Robyn E. Sanderson, Alexander H. Riley, Andreia Carrillo, Jenna Samuel, Emma Tasso

Mathematical Physics · Cross-listed from q-fin.TR

Revisiting Trade-sign Long-memory and Square-root Law price impact

Chris Angstmann and Tim Gebbie

Starting with a coupled discrete reaction–diffusion formulation for the lit and latent order books with non-uniformly sampled event times and meta-order source terms we show how two familiar market-microstructure regularities can emerge from this framework: the long-memory of trade signs associated with the Lillo–Mike–Farmer (LMF) theory and the square-root law (SQRL) of meta-order impact. This uses the locally linear order book and constant participation-rate execution in the front dynamics to reduce the dynamics to a Volterra equation whose leading-order solution then yields the well know result of concave impact trajectory, and a completion impact proportional to the square root of the meta-order size. We then use the interface representation to show how heavy-tailed Pareto meta-order lengths generate power-law trade-sign autocorrelations through the source term. These are familiar derivations, what is slightly different here is that we reinterpret these known derivations to make it clear that LMF law is an event-time sign-memory statement, whereas the square-root law is a physical-time viability statement where subordination can alter the calendar-time impact trajectories depending on the mappings and interpolation used to set continuum operational time.
Read the full abstract

General Relativity and Quantum Cosmology

Interaction of fluids described through relative motion and application to Bianchi type-I spacetimes

Peter Mészáros and Daniel Račko

We study a model of two fluids with an interaction that depends on their relative motion. The interaction is described using the particle number density of each fluid measured in the rest frame of the other, providing a geometric interpretation of a class of interactions studied in relativistic multifluid theory. We derive the corresponding stress-energy tensor and show that its structure agrees with established results. In particular, the interaction introduces a dependence on the scalar product of the $4$-velocities, which can be expressed in terms of the relative speed of the fluid elements. Furthermore, the relative motion produces unequal pressures along and perpendicular to the direction of motion, together with an energy flux. As an application, we consider a Bianchi type-I universe dominated by one fluid, with the second fluid acting as a source of small anisotropy. We examine how the interaction influences the relative speed and the evolution of cosmological anisotropy. We identify conditions under which the anisotropy decays in the late-time limit, generalizing results for non-interacting fluids from the literature.
Read the full abstract

Materials Science

Dynamically suppressed lattice rotations in SrTiO$_3$ as a basis for photo-induced ferroelectricity

Huaiyu Hugo Wang, Michael Fechner, Giovanni De Vecchi et al. (+22 more)

Photo-induced ferroelectricity in the quantum paraelectric SrTiO$_3$ involves the dynamical interplay between a coherently driven Ti-O stretching vibration and multiple structural degrees of freedom, including antiferrodistortive rotations, strain, and the polar mode instability. In the high-temperature cubic phase, in the absence of average antiferrodistortion, time-resolved X-ray diffuse scattering has evidenced a correlation between a photo-induced reduction in antiferrodistortive fluctuations and the emergence of ferroelectric order. Here, we complement these measurements with time-resolved elastic X-ray diffraction in the low-temperature tetragonal phase, in which antiferrodistortive fluctuations are small but a finite average rotation has set in. In this phase, we observe a long-lived reduction of the equilibrium antiferrodistortive rotation angle. A unified theory of the nonlinear lattice dynamics based on first-principles calculations describes the dynamics in both high-temperature cubic and low-temperature tetragonal phases, providing a basis for light-induced ferroelectricity in SrTiO$_3$.
Read the full abstract

All authors Huaiyu Hugo Wang, Michael Fechner, Giovanni De Vecchi, Sylvia L. Griffitt, Gal Orenstein, Jade Stanton, Viktor Krapivin, Man T. Wong, Zhuquan Zhang, Mina Bionta, Vincent Esposito, Meredith Henstridge, Matthias C. Hoffmann, Patrick L. Kramer, Zach Porter, Ryan A. Duncan, Takahiro Sato, Soyeun K. Kim, Hasan Yavas, Samuel Teitelbaum, Keith Nelson, Ankit S. Disa, Michael F"orst, Mariano Trigo, Andrea Cavalleri

Quantum Physics

Bi-qutrit entangled edge states of positive partial transposes with largest ranks

Kyung Hoon Han and Seung-Hyeok Kye

Whenever $E$ is an eight dimensional subspace of the bi-qutrit quantum system whose orthogonal complement is spanned by a vector of Schmidt rank three, we show that there exist PPT entangled edge states with the range space $E$ whose partial transposes are of rank six, which is the largest possible rank. In this way, we exhibit a huge family of bi-qutrit PPT entangled edge states of type $(8,6)$. They make faces of the convex set of all PPT states, and we find bi-qutrit PPT entangled edge states of other types on the boundaries of such faces.
Read the full abstract

Optics

Wavelength-Multiplexed 2D Beam Steering via a Passive Diffractive Network

Che-Yung Shen, Yuhang Li, Cagatay Isil et al. (+3 more)

We introduce a wavelength-addressable diffractive optical network that transforms illumination wavelength into a high-dimensional control parameter for arbitrarily programmable 2D beam steering. The proposed passive architecture comprises cascaded spatially optimized diffractive layers, jointly designed using deep learning, to rapidly map distinct wavelengths to predefined/desired output angles. Unlike conventional single-layer dispersive optical elements, which are physically restricted to 1D linear mapping, this framework harnesses complex wavefront transformations to utilize the illumination wavelength as an intrinsic addressing key for arbitrary 2D beam steering, eliminating the need for mechanical scanning or electronic phase control. We numerically demonstrate wavelength-controlled beam steering across 625 wavelength channels spanning 400-750 nm, realizing a 25 x 25 array of independently addressable beam positions with subwavelength positioning accuracy and high channel fidelity. Unlike conventional gratings, which constrain wavelength routing to a linear trajectory, the proposed diffractive network performs nonlocal wavefront transformations, enabling arbitrary wavelength-to-angle mappings across a 2D field of view. We further validate the proposed framework experimentally in both the terahertz and visible spectral regimes, demonstrating wavelength-multiplexed beam steering using 3D fabricated passive diffractive layers at terahertz frequencies and phase-only spatial light modulators in the visible spectrum. This wavelength-addressable diffractive architecture establishes a compact and scalable paradigm for high-speed programmable beam steering, with potential applications in optical communications, routing, imaging, sensing, and emerging photonic information-processing systems.
Read the full abstract

All authors Che-Yung Shen, Yuhang Li, Cagatay Isil, Tianyi Gan, Mona Jarrahi, Aydogan Ozcan

Superconductivity

Tuning superconductivity and charge density wave order by next-nearest-neighbor hopping integral in honeycomb Holstein model

Hongxing Liu, Lufeng Zhang and Tianxing Ma

By using unbiased determinant quantum Monte Carlo simulations, we investigate the interplay between superconductivity and charge density wave order in the Holstein model on a honeycomb lattice with next-nearest-neighbor hopping \(t^{\prime}\). We find that a finite negative \(t^{\prime}\) enhances \(s\)-wave superconducting pairing susceptibility near the van Hove fillings in the weak electron-phonon coupling regime, while it suppresses superconductivity and promotes charge density wave order at intermediate electron-phonon coupling strengths. The effect of \(t^{\prime}\) on a charge density wave is filling-dependent: It suppresses the charge density wave at half filling but enhances it near the van Hove singularities. A spectral analysis reveals the opening of a gap at low temperatures, highlighting the competitive relationship between superconducting and charge density wave orders mediated by electron-phonon coupling and tuned by \(t^{\prime}\).
Read the full abstract

Statistical Mechanics · Cross-listed from math.PR

Super-Arrhenius relaxation of the triangular plaquette model in any dimension

Laurent Bartholdi, Ivailo Hartarsky and Ivan Mitrofanov

Consider the following plaquette model from statistical physics: a lamp lies at every vertex of the triangular lattice and a switch lies at every even vertex of the (bipartite) dual hexagonal lattice. Each switch toggles the three lamps on its face. The energy of a configuration is the number of ON lamps. For the Glauber dynamics associated with the Gibbs measure defined by this Hamiltonian at any inverse temperature $\beta>0$, we show that, in any dimension $d\ge 2$, the infinite volume relaxation time satisfies \[e^{\beta^2/C}/C \le T_{\mathrm{rel}}\le Ce^{e^{C\beta}}\] for some $C>0$. Our result entails that the Gibbs measure is unique. The $e^{\beta^2}$ scaling was conjectured by Newman and Moore in 1999 and matches the behaviour of supercritical rooted kinetically constrained models such as the East model, thus recovering fragile glass phenomenology in the absence of kinetic constraints. More precisely, we show that, on a torus of side length $2^k$, when $\beta\to\infty$ and $k/\beta\to0$, we have $T_{\mathrm{rel}}=e^{2\beta k(1+o(1))}$. Quite surprisingly, however, we also prove that, on non-periodic finite domains of size $n\le e^{\beta/C}$ for large $C>0$, we have the much larger asymptotics $\ln T_{\mathrm{rel}}=\beta n^{\Theta(1)}$. The main ingredients of the proofs are new results in extremal and enumerative combinatorics and rely on renormalisation ideas for the dynamics and its groundstates also known as the Ledrappier subshift. We note consequences of our results to geometric group theory (more precisely to the complexity of the word problem for the Baumslag finitely presented group) and to ergodic theory.
Read the full abstract

Nuclear Experiment

Evidence for a $\bar{K}NN$ quasi-bound state in the $\gamma d \to K^0\Lambda p$ reaction

R. Kobayakawa, J. K. Ahn, S. Ajimura et al. (+34 more)

The $\gamma d \to K^{0}\Lambda p$ reaction has been studied to search for a $\bar{K}NN$ quasi-bound state using the LEPS2 solenoid spectrometer at SPring-8. A localized enhancement concentrated at low $q$ is observed in the $(M_{\Lambda p},q)$ distribution below the $K^-pp$ mass threshold, where $M_{\Lambda p}$ is the $\Lambda p$ invariant mass and $q \equiv |\vec{p}_{\gamma}-\vec{p}_{K^{0}}| = |\vec{p}_{\Lambda p}|$ is the momentum transfer. A two-dimensional $(M_{\Lambda p},q)$ fit demonstrates that the enhancement near the threshold is statistically significant, yielding a local significance of $7.3,\sigma$. The enhancement is characterized by effective shape parameters including the Breit–Wigner mass $M$ and width $\Gamma$, and a Gaussian form-factor momentum scale $Q$: $M = 2.354 \pm 0.011(\mathrm{stat.})^{+0.009}_{-0.005}(\mathrm{syst.})~\mathrm{GeV}/c^{2}$, $\Gamma = 0.055 \pm 0.023(\mathrm{stat.})^{+0.031}_{-0.009}(\mathrm{syst.})~\mathrm{GeV}/c^{2}$, and $Q = 0.350 \pm 0.041(\mathrm{stat.})^{+0.035}_{-0.010}(\mathrm{syst.})~\mathrm{GeV}/c$. The obtained results support the existence of a $\bar{K}NN$ quasi-bound state in photoproduction.
Read the full abstract

All authors R. Kobayakawa, J. K. Ahn, S. Ajimura, W.-C. Chang, M.-L. Chu, S. Daté, T. Gogami, T. A. Hashimoto, T. Hotta, T. Ishikawa, H. Katsuragawa, H. Kohri, Y. Ma, M. Miyabe, K. Mizutani, N. Muramatsu, T. Nakano, T. H. Nam, M. Niiyama, Y. Nozawa, Y. Ohashi, H. Ohkuma, H. Ohnishi, T. Ohta, C. Rangacharyulu, S. Y. Ryu, Y. Sada, H. Shimizu, M. Sumihama, S. Suzuki, S. Tanaka, A. O. Tokiyasu, N. Tomida, K. Watanabe, T. Yorita, C. Yoshida, M. Yosoi

Solar and Stellar Astrophysics

Near-Sun Switchbacks Show Statistical Signatures of Solar Activity

Sneha Pandit, Thierry Dudok de Wit, Clara Froment et al. (+3 more)

The large amplitude, Alfvénic deflections in the solar wind, called magnetic switchbacks, are a ubiquitous feature of the inner heliosphere, yet their origin and variability remain poorly understood. We investigate the dependence of large amplitude magnetic fluctuations in the inner heliosphere on both heliocentric distance and global solar activity. Using Parker Solar Probe observations, we quantify switchback deflections through their normalised deflection angle $z$. We examine both their distribution and the probability of large events, combining radial binning, sunspot-number-based activity classification, and regression analysis. We find a statistically significant but weak dependence of switchback properties on solar activity, with a decrease in large deflections at higher activity levels, alongside a modest increase with heliocentric distance. The weak activity trend suggests that multiple processes act simultaneously. Solar-cycle variations in coronal magnetic topology may modulate switchback generation at the source, while nonlinear in situ effects in the solar wind may partially evolve these signatures. Our results indicate that switchbacks retain only a limited imprint of solar activity, reflecting a coupled interplay between coronal origin and in situ evolution. This study provides a quantitative framework to disentangle activity and radial effects, and highlights the need for multi-parameter and multi-spacecraft analyses to fully understand the origin and evolution of switchbacks.
Read the full abstract

All authors Sneha Pandit, Thierry Dudok de Wit, Clara Froment, Durgesh Tripathi, Vishal Upendran, Gabriel Ho Hin Suen

Strongly Correlated Electrons

Multiband transport hierarchy and large Nernst effect in EuAuBi: Establishing a Nernst scaling for asymmetric multiband systems

Weimin Quan, Xiaodong Guo, Lingxiao Zhao et al. (+4 more)

In correlated materials, coexisting pockets of vastly different carrier densities raise two fundamental questions: which pocket governs the various transport coefficients, and does the conventional Nernst scaling $\nu/T \propto \mu/E_F$, originally derived for single-band systems, still hold? We address both questions in the polar semimetal EuAuBi, where a dilute electron pocket ($n_e \sim 10^{16}~\mathrm{cm}^{-3}$) coexists with a dense hole pocket ($n_h \sim 10^{21}~\mathrm{cm}^{-3}$). We find a clear hierarchy: the hole pocket dominates the longitudinal resistivity; the Hall effect crosses from electron- to hole-dominance with increasing field; the Seebeck coefficient is dominated by the electron pocket at low temperature and by both pockets at high temperature. Remarkably, the Nernst effect is governed entirely by the ultrahigh-mobility electron pocket, yielding a large low-field signal of $\sim 5~\mu\mathrm{V/K}$ near 1~T at 202~K, comparable to anomalous Nernst signals in magnetic Weyl semimetals. By analyzing the two-band thermoelectric conductivity, we show that the Nernst coefficient follows a scaling $\nu/T \propto \mu_e/{E_{F, tot}}$. This scaling originates from a compensation between the electron-to-hole conductivity ratio and the Fermi-energy ratio, establishing that the large Nernst effect is a semiclassical multiband phenomenon rather than a topological Berry-curvature contribution. This understanding advances the thermoelectric transport physics of multiband electronic systems and offers a guiding principle for low-field transverse thermoelectric design.
Read the full abstract

All authors Weimin Quan, Xiaodong Guo, Lingxiao Zhao, Shengwei Chi, Gang Xu, Zengwei Zhu, Xiaokang Li

Cosmology and Nongalactic Astrophysics

Benchmarking Exact, GP-Emulated, and Simulation-Based Inference for Late-Time Cosmology

Sai Swagat Mishra

Forthcoming cosmological surveys require inference pipelines that are both statistically reliable and computationally scalable. In this work, we perform a systematic comparison of three complementary inference strategies for late-time $\Lambda$CDM cosmology: exact Markov Chain Monte Carlo (MCMC), Gaussian Process (GP)-assisted MCMC, and neural Simulation-Based Inference (SBI). Using a common analysis framework based on Cosmic Chronometers, DESI DR2 baryon acoustic oscillation measurements, and the Pantheon+ Type Ia supernova compilation, we consider two dataset combinations of increasing complexity, namely CC+DESI and CC+DESI+PP, under identical cosmological assumptions and priors. For CC+DESI, both GP emulation and SBI reproduce the exact posterior constraints on $(H_0,\Omega_{m,0})$ to better than $0.3\sigma$. For the more constraining CC+DESI+PP combination, modest method-dependent shifts emerge, reaching at most $\sim1.5\sigma$ in a single parameter. Despite these differences, all methods recover a nearly identical expansion history, with percent-level agreement across the full redshift range. From a computational perspective, GP emulation accelerates model evaluations but remains limited by MCMC sampling, whereas SBI achieves order-of-magnitude reductions in total runtime through amortized posterior learning. We further investigate the convergence of SBI as a function of simulation budget and identify the number of simulations required to obtain stable posterior constraints. Overall, our results demonstrate that accelerated inference techniques can deliver reliable cosmological constraints for realistic late-time datasets considered here at a fraction of the computational cost of conventional likelihood-based analyses.
Read the full abstract

Strongly Correlated Electrons

Orbital-selective band evolution and out-of-plane correlation in the FeGe-family kagome antiferromagnet ScFe$_6$Ge$_6$

Jae Hyuck Lee, Ze Yan, Tongrui Li et al. (+10 more)

In strongly correlated materials such as high-temperature superconductors, the relation between charge density wave (CDW) order and magnetism remains an important unresolved problem. FeGe is the first kagome metal known to exhibit CDW order deep within an antiferromagnetic state, accompanied by an unconventional evolution of lattice symmetry. To elucidate the general conditions governing such spin-correlated CDW order, we investigate ScFe$_6$Ge$_6$, which lacks CDW order and therefore exhibits reduced involvement of charge degrees of freedom while retaining other properties of FeGe. Instead of a CDW order, ScFe$_6$Ge$_6$ undergoes a magnetic transition at $T^*$ = 195 K. Across this transition, angle-resolved photoemission and Raman spectroscopy reveal orbital-selective behavior confined to a single kagome Dirac band, together with electron-phonon and magnetoelastic coupling to an out-of-plane phonon mode. These results suggest that orbital-selective physics and out-of-plane correlations play enhanced roles in realizing spin-correlated CDW order in magnetic kagome metals.
Read the full abstract

All authors Jae Hyuck Lee, Ze Yan, Tongrui Li, Yichen Yang, Dirk Wulferding, Jongkeun Jung, Zhicheng Jiang, Mao Ye, Zhengtai Liu, Changyoung Kim, Soohyun Cho, Yanfeng Guo, Dawei Shen

Strongly Correlated Electrons

Interfacial control of magnetism and electron transport in nonisostructural SrRuO$_3$/SrCuO$_2$ heterostructure

Digbijaya Palai, B. Maharana, P. Biswal et al. (+7 more)

Heterointerfaces between structurally dissimilar oxides provide a platform to exploit the interfacial mismatch in the lattice and electronic degrees of freedom to realize emergent functionalities and tunable physical properties with potential applications in oxide electronics. Here, we investigate the magnetic and electronic transport properties of symmetry-mismatched SrRuO$_3$ (SRO)/SrCuO$_2$ (SCO) heterostructure, in which a 4-nm-thick itinerant ferromagnetic metal SRO is interfaced with a planar-type antiferromagnetic insulator SCO, in comparison with a reference SRO (4 nm) film. While both the bare SRO and SRO/SCO bilayer exhibit perpendicular magnetic anisotropy (PMA), the SRO/SCO bilayer shows a pronounced enhancement in the saturation magnetization (M$_S$ $\approx$ 2.7 $\mu_B$/Ru) and effective anisotropy constant (K$_{\mathrm{eff}}$ $\approx$ 2.13 $\times$ 10$^6$ erg/cc) relative to the bare SRO film (M$_S$ $\approx$ 1.3 $\mu_B$/Ru and K$_{\mathrm{eff}}$ $\approx$ 5.25 $\times$ 10$^5$ erg/cc). Interestingly, the low-temperature resistivity upturn below 5 K arising from disorder-induced quantum corrections in bare SRO is strongly suppressed in SRO/SCO, and it exhibits Fermi-liquid-like transport ($\rho \propto T^2$) down to 2 K. Analysis of the anomalous Hall effect (AHE) reveals dominant intrinsic Berry-curvature driven electron transport in both samples, with enhanced intrinsic and skew-scattering contributions in the SRO/SCO bilayer, indicating the critical role of the interface in modifying the electronic band structure near the Fermi level. Our results demonstrate that the interface acts as an effective control knob, concurrently enhancing the magnetization, PMA, and intrinsic scattering contribution to the AHE in the SRO/SCO heterostructure, while suppressing the disorder-driven quantum corrections to transport behavior observed in the bare SRO film.
Read the full abstract

All authors Digbijaya Palai, B. Maharana, P. Biswal, Shwetha G. Bhat, D. Nayak, D. Sahoo, R. Soni, K. Senapati, Z. Hossain, D. Samal

Mesoscale and Nanoscale Physics

Hidden chirality and half-vortex formation in exciton-polariton condensates

A. N. Osipov, I. Y. Chestnov, P. G. Lagoudakis et al. (+1 more)

We show that a radially symmetric, nonresonantly pumped spinor exciton-polariton condensate can acquire chirality without a rotating drive, chiral geometry, or pump orbital angular momentum. Spin relaxation in a two-reservoir system shifts the reservoir-induced blueshift relative to the gain profile, creating an effective non-Hermitian chiral potential. A reduced angular-mode theory reveals tunable exceptional points and non-reciprocal coupling between counter-rotating modes. Full driven-dissipative Gross-Pitaevskii simulations show that this hidden chirality enables all-optical formation of spin-selective half-vortices.
Read the full abstract

All authors A. N. Osipov, I. Y. Chestnov, P. G. Lagoudakis, A. V. Yulin

High Energy Astrophysical Phenomena

Discovery of Unusual Jet Orientation Variations in the Microquasar GRS 1915+105

Xi Yan, Lang Cui, Wu Jiang et al. (+6 more)

We report large day-timescale variations in the orientation of the southeast–northwest jet in the prototype microquasar GRS 1915+105. These results are based on three-epoch East Asia VLBI Network (EAVN) observations at 6.7 GHz, obtained during giant radio flares in 2025 detected by the RATAN-600 monitoring program. Our observations reveal the smallest position angle (PA) of $118^\circ \pm 7^\circ$ ever measured for the jet in GRS 1915+105, which increases to $152^\circ \pm 2^\circ$ within 37 days. Based on the literature results, we further suggest that the jet orientation has exhibited significant variations over a PA range of $118^\circ$–$188^\circ$ since 2023. This unusual jet orientation behavior in GRS 1915+105 during its current X-ray-obscured state may arise from a warped, precessing inner accretion disk, as implied by recent X-ray spectroscopy. Notably, one image reveals a peculiar morphology in GRS 1915+105, which likely indicates lateral spreading of the approaching southeast jet. Future observations are essential to clarify the issues raised in this work.
Read the full abstract

All authors Xi Yan, Lang Cui, Wu Jiang, Zhen Yan, Sándor Frey, Sergei Trushkin, Timur Mufakharov, Ruchika Dhaka, Shuangjing Xu